Tracking Easy Gainers

Residual feed intake (RFI) is the new buzzword in the beef industry. Simply put, it measures metabolic efficiency, so you'll hear it expressed as a performance trait.

"RFI measures how efficiently an animal converts what it eats into maintenance and growth," says University of Missouri nutritionist Monty Kerley.

"We've always looked at feed efficiency as a conversion of feed to gain. The problem is that producers continually selecting for this sort of conversion get lean growth, and animals just keep getting bigger.

"With RFI," Kerley continues, "the emphasis is on individual animal efficiency. We can see how efficiently each animal is using the energy it consumes. "With nearly every group of calves, we'll typically see a 40% difference in RFI between the least and the most efficient individuals in the group, while actual gains may be very similar," says Kerley.

A 40% difference in RFI equates to a difference of 40% in feed costs. When averaging extremes across a cow herd, for example, "The least efficient one-third of the herd will consume 20% more forage than the most efficient one-third," says Kerley. The high cost of feed is one factor driving the current interest in RFI.

"For the first time in a long time, the cost of feed is the determining factor in feedlot profit," he says.

Also fueling interest is new technology that can test individual animals within whole pens of cattle.

One line of equipment uses bunkline feeders with individual stanchions and feeding compartments. Feeders are fitted with weighing mechanisms.

An electronic tag identifies each animal. As the animal eats at the feeder, a sensor reads the tag number while a built-in weighing mechanism records the weight of the feed eaten and correlates the amount with the tag number.

Since it's so expensive, individual RFI testing is more likely to show up in bull test centers rather than commercial feedlots. A handful of these centers are already offering the service to purebred breeders.

Best use of RFI in genetic selection for efficiency will be as a balance to the trait for growth.

"Phenomenally efficient animals may not grow very well," Kerley cautions. "You want animals that metabolize efficiently but you also want animals that have growth performance."

While limited data suggest that females with efficient RFIs take a few days longer to breed back, "it appears that selecting for the trait has no significant negative effect on any other traits," says Kerley.

Learn More: Monty Kerley 573/882-0834 kerleym@missouri.edu

Residual feed intake (RFI) is the new buzzword in the beef industry. Simply put, it measures metabolic efficiency, so you'll hear it expressed as a performance trait.